High-voltage-measuring instrument.



I. B. WHITEHEAD.. HTGH VOLTAGE MEASURING INSTRUMENT.

APPLICATION FILED APR. 29. I9I6.

Patented Mar. 19, 1918.

@uve/Moz J. Wwfeh l lm.I I

i 'f if i 'i HIGH-VOLTAGE-MEASURING INSTRUMENT.

Specification of Letters Patent.

Patented Mar. 19, 1918.

Application led April 29, 1916. Serial No. 94,443.

. a citizen of the United States, residing at Baltimore city, and 'State of Maryland, have invented certain new and useful Improvements in High-Voltage-Measuring Instruments, of which the following'is a specification.

This invention relates to improvements in that type of high voltageV measuring instrument described and set forth inU. S. Patent No. 1,059,095, granted tome April 15,

1913, in which the voltage is determined by the presence of corona on a round wire placed centrally in an outer cylinder.

For a wire of single uniform diameter in an outer tube of given diameter, the corona will appear at a given voltage determined by the diameter of wire and outer cylinder, and by the density of the gas or air sur,- rounding the wire. Consequently, if the instrument is operated at one pressure (e. g., atmospheric pressure), for a given temperature, only one value of the voltage could be read.V In order to extend the range of the instrument, it was proposed. in my patent l above referred to that the central wire could be changed. giving another diameter, hence another voltage. It was also stated that a conical wire or a wire having -several .sections of diferent diameters could be used for this purpose.

The principal object of the present invention is to provide means for extending the range of the instrument without reference to a change in the diameter of the central wire, and in doing this advantage is taken of the influence of the density of the gas or air at which corona forms. This density may be varied by varying either the pressure or the temperature of the gas or air. Increasing the pressure increases'the voltage at which corona appears, that is to say, retards the corona, and increasing temperature lowers the corona voltage, that 1s, accelerates its appearance. The e'ects of both temperature and pressure are combined in one correction factor known as the density factor. In the instrument here shown, the change of density is effected by changing the air or gas pressure, and for this purpose the cylinderabove referred to and its central wire are inclosed in an air tight tube or casing, and means are provided for either increasing or decreasing the air pressure in the tube or casing, and also for reading the values of the temperature and pressure therein, from which the exact value of the density, and, therefore, by 'known laws the exact value of the voltage, may be determined.

The present invention further provides improved means for telling when the corona first appears. This consists in locating atelephone transmitter inside the outer cylinder or casing and connecting this to a telephone receiver. The instant that corona appears on the central conductor, a sound is transmitted to the telephone receiver. There are several other ways of indicating the presence of the corona, such, for example, as by an electroscope, galvanometer, or visually, that is, noting its presence directly with the eye, as by observing the wire through an opening in the tube; but none of these is here claimed, as theyare fully set forth in .my said patent. It should be understood, however, that any of these methods may be substituted in the present instrument for the telephonie detector shown. In fact, I prefer to equip the instrument with means for operating with two or more of these methods, in case for any reason one should get out of order.

Since the temperature will vary through narrow limits depending on the season and location 'in which the instrument is used, the tables or curves which are provided will giveA for each temperature the values of the pressure which will be necessary for any desired value of air density.

In .order to more fully describe my invention, reference will be had to the accompa' nying drawing which shows in vertical central section one embodiment thereof.

In the accompanying drawing, 1 represents the central wire which is circular in cross sectionv and of uniform diameter, 2 the inner metal cylinder, and 3 the outer tube or casing inclosing the parts mentioned, and consisting of a metal cylinder. The wire 1 extends through and is supported by two insulating bushings 4; and 5 inserted in end plates 6 and 7 which form air tight closures for opposite ends of casing 3, said wire coinciding with the central longitudinal axis of cylinder 2, that is, concentrically therein. The cylinder 2 is supported within casing 3 by metal supports 8 and 9 fast to the outer casing 3.

There is provided at a suitable point,an opening 10, .through the wall of casing 3,

into which extends a pipe 11 which leads from a pressure or vacuum pump or from any other desired source of air under pressure or vacuum. For purposes of illustra'- tion, I have indicated an air tank 12, connected to pipe 11, and which we may assume contains air under pressure. 13 indicates a gage showing the air pressure within the casing3, and 14 a valve whereby this pressure may be varied. By openingwvalve 14 air under pressure from storage tank 12 may be admitted to the interior of casing 3, thus increasing the air pressure therein. A valve 14 may be provided for reducing this pressure. 1

For indicating the temperatures within casing 3, there is provided a thermometer 15 having its bulb within said casing, and its scale extending to the exterior thereof for observation.

The voltage is measured between conductors 16 and 17, leading respectivel from wire 1 and casing 3, the conductor l; being grounded as shown.

The telephone transmitter 18, for detecting the presence of corona, is located, in the instrument shown, in a pocket formed byl a lateral tube 19 screwed into an opening through the wall of casing 3, and closed at one end byl a cap 20 on which the trans mitter is supported. This transmitter is connected through suitable conductors 21 vand battery 22 to a telephone transmitter 23 outside of tube 3.

The appearance of corona may also be detected visually, for which purpose there is provided a tube 24 which extends into an opening near the bottom of casing 3, said tube being closed at its outer end by a glass or transparent closure 25 forming a window through which'may be viewed the corona as it appears on conductor 1.

The instrument may be used in several ways: For example, a voltage can be applied to the terminals when quite high pressure exists inside casing 3. This pressure is then gradually lowered, which may be effected by opening valve 14', until corona appears. The value of the pressure and temperature within casing 3, and the physical dimensions of the instrument (diameter of wire 1 and inside diameter of tube 2) will then determine denitely the voltage.

. Tables and curves are provided for immediate determination of the voltage-from these values.

In testingthe insulation of machinery, it is often desirable to set the voltage-at a given value. vThis given value in the present instrument will cause corona to appear vat a definite pressure. The pressure will be adjusted to this value, and the voltage gradually raised until corona appears. This voltage has the desired value.-

While I have herein shown but one specific embodiment of my invention, it will be understood that modifications thereof may be made within the scope of what I claim, and in the accompanying' claims the expression critical surface intensityy is used to mean the voltage gradient at the surface of the conductor at which visible corona appears and ionization of the neighboring air with accompanying conductivity begins.

What I claim. is:

1. A high voltage measuring instrument of the class described, comprising two electrical conductors, one of which surrounds the other with an air space therebetween,` and means to vary the density of the air or gas within saidspace to vary the critical surface intensity of one of said conductors.

2. A high voltage measuring instrument of the class described, comprising two electrical conductors, one of which surrounds the other with an air space therebetween,

and means to vary the pressure of the air or gas within said space to vary the critical surface intensity of one of said conductors.

3. A high voltage measuring instrument of the class described, comprising two electrical conductors, one of which surrounds the-,other with .an air space therebetween, means to indicate the temperature andpressure of the air within said space, and means to vary the pressure of the air or as within said space to vary the critical surl ace intensity of one of said conductors.

4. A high voltage measuring instrument of the class described, comprising two electrical conductors, one of which surrounds the other with an air space therebetween, a casing inclosing said conductors, and means to vary the density of the air or gas within said casing to vary the critical surface intensity of one of said conductors.

5. A high voltage measuring instrument of the class described, comprising a metallic tube, an electrical conductor extending axially through said tube and separated there-` from by an air space, insulating supports for said conductor, an air tight casing surrounding said tube and separated therefrom by an air space, and means to vary the density of air or gas within said casing to vary the critical surface intensity of said conductor.

' 6. 4A high voltage measuring instrument of the class described, comprising a 'metallic tube, an electrical conductor extending axially through said tube and separated therefrom by an air space, insulating supports for said conductor, an air tight casing surrounding said tube and separated therefrom by an air space, a source of air or gas under pressure connected to the interior of said casing, and means to vary the pressure.- of the air or gas within said casing to vary the critical surface intensity of conductor.

naseee 7. A high voltage measuring instrument of the class described, comprisingan electrical conductor, means to determine the value of voltage applied thereto by the presence of corona about said conductor, said y means including a telephone transmitter located in proximity to said conductor and responsive to the presence of said corona.

8. A high voltage measuring instrument of the class described, comprising a metallic tube, an electrical conductor extending axially through s aid'tube and separatedvtherefrom by an air space, insulating supports for said conductor, an air tight ca surltelephone receiver exterior to y said casing 2@ y operatively connected with said transmitter. In testimony whereof I ax my signature in the presence-'of two witnesses.

JOHN B. WTEHE.

Witnesses:

A. Lien NICHOLSON,

im t J; GY. 

